Characterization of a mobile radio channel plays an important role in designing a reliable wireless communication system. Such channels are analyzed by two state model, namely satisfactory and outage state. This paper...Characterization of a mobile radio channel plays an important role in designing a reliable wireless communication system. Such channels are analyzed by two state model, namely satisfactory and outage state. This paper presents the analysis to estimate fading parameters of wireless channel with omission of certain outage durations which are considered as “Tolerance time”. Minimum outage duration which can be tolerated by a wireless fading channel to achieve desired packet error rate is defined as tolerance time. Normally a system with tolerable minimum outage time is analyzed based on Fade Duration Distribution (FDD) function over Rayleigh channel. In this paper Weibull function is used as FDD for varying tolerance time. The approach is simple and in general applicable from Rayleigh to Nakagami channels. The analysis is extended to study the effect of Tolerance time on channel fading statistics such as Average Fade Duration (AFD) and frequency of outage. Further the effects of various fade margin and Doppler spread on fading parameters are also investigated. The analysis can also be used in case of timeout expiration, connection resetting and congestion window control.展开更多
For differential phase shift keying （DPSK） and noncoherent frequency shift keying （NFSK） systems over fading channels, the post-detection combining method is a popular means for improving the bit error performance...For differential phase shift keying （DPSK） and noncoherent frequency shift keying （NFSK） systems over fading channels, the post-detection combining method is a popular means for improving the bit error performance. However, the bit error performance of such systems over Nakagami channels with an arbitrary covariance matrix and real distinct fading parameters has been seldom described in the literature. This paper studies the problem using a generic correlated Nakagami fading model and presents a closed form solution which is used to study the influence of the fading parameters and the signal-to-noise ratio （SNR） distribution ratios among all the branches on the bit error performance. Moreover, the average SNRs of each branch are not restricted to one value in the analysis. The closed form solution developed for the problem can be used to study the influence of the fading parameters and the SNR distribution ratios on the error performance.展开更多
Based on the Maximum-Likelihood (ML) criterion, this paper proposes a novel noncoherent detection algorithm for Orthogonal Multicode (OM) system in Nakagami fading channel. Some theoretical analysis and simulation res...Based on the Maximum-Likelihood (ML) criterion, this paper proposes a novel noncoherent detection algorithm for Orthogonal Multicode (OM) system in Nakagami fading channel. Some theoretical analysis and simulation results are presented. It is shown that the proposed ML algorithm is at least 0.7 dB better than the conventional Matched-Filter (MF) algorithm for uncoded systems, in both non-fading and fading channels. For the consideration of practical application, it is further simplified in complexity. Compared with the original ML algorithm, the simplified ML algorithm can provide significant reduction in complexity with small degradation in performance.展开更多
Decision fusion rules for Wireless Sensor Networks (WSNs) under Nakagami fading channels are investigated in this paper. Considering the application limitation of Likelihood Ratio Test fusion rule based on information...Decision fusion rules for Wireless Sensor Networks (WSNs) under Nakagami fading channels are investigated in this paper. Considering the application limitation of Likelihood Ratio Test fusion rule based on information of Channel Statistics using Series expansion (LRT-CSS),and the detection performance limitation of the Censoring based Mixed Fusion rule (CMF),a new LRT fusion rule based on information of channel statistics has been presented using Laplace approximation (LRT-CSL). Theoretical analysis and simulations show that the proposed fusion rule provides better detection performance than the Censoring based Mixed Fusion (CMF) and LRT-CSS fusion rules. Furthermore,compared with LRT-CSS fusion rule,the proposed fusion rule expands the application range of likelihood ratio test fusion rule.展开更多
Space-Time Frequency (STF) codes for MIMO-OFDM over block-fading channel can achieve rate?? Mt and full-diversity Mt Mr Mb L which is the product of the number of transmit antennas Mt, receive antennas Mr, fading bloc...Space-Time Frequency (STF) codes for MIMO-OFDM over block-fading channel can achieve rate?? Mt and full-diversity Mt Mr Mb L which is the product of the number of transmit antennas Mt, receive antennas Mr, fading blocks Mb and channel taps L. In this article, time permutation is proposed to provide independent block-fading over Jake’s Doppler power spectrum channel. Moreover, we show the performance variations of STF code as channel delay spread changes. Therefore, we introduce a frequency/time permutation technique in order to remove the frequency correlation among sub-carriers, which subsequently increases the coding gain and achieves maximum diversity. Finally, the symbol error rate (SER) performance of the proposed time/frequency permuted STF codes over independent and correlated MIMO antenna branches under Nakagami fading channel is simulated. We show that the proposed systems provide better performance and more robust to large values of antennas correlation coefficients in comparison with the un-interleaved one.展开更多
This paper proposes a modified decodeand-forward(DAF) protocol with a three-node model,which contains two users and one destination.Each user can be either the source or the relay in different frames.We analyze the fo...This paper proposes a modified decodeand-forward(DAF) protocol with a three-node model,which contains two users and one destination.Each user can be either the source or the relay in different frames.We analyze the four cooperative cases in the first frame and run simulations to obtain the optimal power allocation coefficients in the second frame.The closed-form expression of outage probability is derived over Nakagami-m fading channels.Furthermore,we show that the proposed model has better performance than the non-cooperation system and traditional DAF strategy based on the derived outage probability.展开更多
The different realistic propagation channels are faced frequently the multipath fading environments. The main goal of this system design (cognitive radio network) is to improve the efficiency of spectrum access on a n...The different realistic propagation channels are faced frequently the multipath fading environments. The main goal of this system design (cognitive radio network) is to improve the efficiency of spectrum access on a non-interfering basis. This system achieves high utilization for the limited spectrum in order to fulfill needs for all users’ demands which are considered as a problem in wireless communications due to rapidly increasing in wireless applications and service. This system is exposed to attack due to the vulnerabilities existence in this system. So, the main outcome of this paper is to investigate the performance of the cooperative sensing in cognitive radio networks under malicious attacks over different channel impairments, and to illustrate the most suitable individual probability of detection in real faded channel by using Nakagami model. This paper illustrates the effectiveness of the attacks and fading on the performance of spectrum sensing process.展开更多
分集技术可有效提高无线通信系统抗衰落性能,通过将Nakagami衰落下的分集系统等效为单输入单输出系统,推导获得了选择合并(Selection combining,SC)、等增益合并(Equal gain combining,EGC)和最大比合并(Maximal ratio combining,MRC)3...分集技术可有效提高无线通信系统抗衰落性能,通过将Nakagami衰落下的分集系统等效为单输入单输出系统,推导获得了选择合并(Selection combining,SC)、等增益合并(Equal gain combining,EGC)和最大比合并(Maximal ratio combining,MRC)3种方式下系统的输出信噪比和中断概率等性能表达式,并提出一种基于改进的Nakagami分集信道舍弃法模型用于数值仿真与验证。仿真结果表明,理论表达式结果与仿真值非常吻合,可用于辅助瑞利、莱斯和Nakagami等多种信道衰落下分集系统的参数选择、算法设计和性能评估。展开更多
文摘Characterization of a mobile radio channel plays an important role in designing a reliable wireless communication system. Such channels are analyzed by two state model, namely satisfactory and outage state. This paper presents the analysis to estimate fading parameters of wireless channel with omission of certain outage durations which are considered as “Tolerance time”. Minimum outage duration which can be tolerated by a wireless fading channel to achieve desired packet error rate is defined as tolerance time. Normally a system with tolerable minimum outage time is analyzed based on Fade Duration Distribution (FDD) function over Rayleigh channel. In this paper Weibull function is used as FDD for varying tolerance time. The approach is simple and in general applicable from Rayleigh to Nakagami channels. The analysis is extended to study the effect of Tolerance time on channel fading statistics such as Average Fade Duration (AFD) and frequency of outage. Further the effects of various fade margin and Doppler spread on fading parameters are also investigated. The analysis can also be used in case of timeout expiration, connection resetting and congestion window control.
文摘For differential phase shift keying （DPSK） and noncoherent frequency shift keying （NFSK） systems over fading channels, the post-detection combining method is a popular means for improving the bit error performance. However, the bit error performance of such systems over Nakagami channels with an arbitrary covariance matrix and real distinct fading parameters has been seldom described in the literature. This paper studies the problem using a generic correlated Nakagami fading model and presents a closed form solution which is used to study the influence of the fading parameters and the signal-to-noise ratio （SNR） distribution ratios among all the branches on the bit error performance. Moreover, the average SNRs of each branch are not restricted to one value in the analysis. The closed form solution developed for the problem can be used to study the influence of the fading parameters and the SNR distribution ratios on the error performance.
文摘Based on the Maximum-Likelihood (ML) criterion, this paper proposes a novel noncoherent detection algorithm for Orthogonal Multicode (OM) system in Nakagami fading channel. Some theoretical analysis and simulation results are presented. It is shown that the proposed ML algorithm is at least 0.7 dB better than the conventional Matched-Filter (MF) algorithm for uncoded systems, in both non-fading and fading channels. For the consideration of practical application, it is further simplified in complexity. Compared with the original ML algorithm, the simplified ML algorithm can provide significant reduction in complexity with small degradation in performance.
基金Supported by the National Natural Science Foundation of China (No.60772139)
文摘Decision fusion rules for Wireless Sensor Networks (WSNs) under Nakagami fading channels are investigated in this paper. Considering the application limitation of Likelihood Ratio Test fusion rule based on information of Channel Statistics using Series expansion (LRT-CSS),and the detection performance limitation of the Censoring based Mixed Fusion rule (CMF),a new LRT fusion rule based on information of channel statistics has been presented using Laplace approximation (LRT-CSL). Theoretical analysis and simulations show that the proposed fusion rule provides better detection performance than the Censoring based Mixed Fusion (CMF) and LRT-CSS fusion rules. Furthermore,compared with LRT-CSS fusion rule,the proposed fusion rule expands the application range of likelihood ratio test fusion rule.
文摘Space-Time Frequency (STF) codes for MIMO-OFDM over block-fading channel can achieve rate?? Mt and full-diversity Mt Mr Mb L which is the product of the number of transmit antennas Mt, receive antennas Mr, fading blocks Mb and channel taps L. In this article, time permutation is proposed to provide independent block-fading over Jake’s Doppler power spectrum channel. Moreover, we show the performance variations of STF code as channel delay spread changes. Therefore, we introduce a frequency/time permutation technique in order to remove the frequency correlation among sub-carriers, which subsequently increases the coding gain and achieves maximum diversity. Finally, the symbol error rate (SER) performance of the proposed time/frequency permuted STF codes over independent and correlated MIMO antenna branches under Nakagami fading channel is simulated. We show that the proposed systems provide better performance and more robust to large values of antennas correlation coefficients in comparison with the un-interleaved one.
基金supported by Major National Science & Technology Specific Project under Grant No. 2009ZX03003-003-01
文摘This paper proposes a modified decodeand-forward(DAF) protocol with a three-node model,which contains two users and one destination.Each user can be either the source or the relay in different frames.We analyze the four cooperative cases in the first frame and run simulations to obtain the optimal power allocation coefficients in the second frame.The closed-form expression of outage probability is derived over Nakagami-m fading channels.Furthermore,we show that the proposed model has better performance than the non-cooperation system and traditional DAF strategy based on the derived outage probability.
文摘The different realistic propagation channels are faced frequently the multipath fading environments. The main goal of this system design (cognitive radio network) is to improve the efficiency of spectrum access on a non-interfering basis. This system achieves high utilization for the limited spectrum in order to fulfill needs for all users’ demands which are considered as a problem in wireless communications due to rapidly increasing in wireless applications and service. This system is exposed to attack due to the vulnerabilities existence in this system. So, the main outcome of this paper is to investigate the performance of the cooperative sensing in cognitive radio networks under malicious attacks over different channel impairments, and to illustrate the most suitable individual probability of detection in real faded channel by using Nakagami model. This paper illustrates the effectiveness of the attacks and fading on the performance of spectrum sensing process.
文摘分集技术可有效提高无线通信系统抗衰落性能,通过将Nakagami衰落下的分集系统等效为单输入单输出系统,推导获得了选择合并(Selection combining,SC)、等增益合并(Equal gain combining,EGC)和最大比合并(Maximal ratio combining,MRC)3种方式下系统的输出信噪比和中断概率等性能表达式,并提出一种基于改进的Nakagami分集信道舍弃法模型用于数值仿真与验证。仿真结果表明,理论表达式结果与仿真值非常吻合,可用于辅助瑞利、莱斯和Nakagami等多种信道衰落下分集系统的参数选择、算法设计和性能评估。
